Weight reduction in all types of vehicles, including motorized vehicles, it) is an approach to improve the energy efficiency of vehicles. Glass reinforced plastics have been a key candidate to replace metal to reduce weight of vehicles. A plastic wheel rim is one example. Low density reinforced plastics have been a key factor for plastic wheels in bicycle, all terrain-vehicle (ATV), utility vehicle (UTV), and potentially automotive vehicle.
However, thermoplastics have lower strength and modulus compared to metal. Fiber reinforcement significantly improves strength and modulus of thermoplastics but reduces elongation at break and ultimately makes plastic more brittle. It is desirable to have a reinforced thermoplastic with high strength, high stiffness; and high elongation. Most 30˜40 weight percent fiber reinforced thermoplastic polyamides and other polymers give 10˜12 Gpa tensile modulus and 2.5˜3.0% elongation at break.
U.S. Pat. No. 4,072,358 discloses a compression molded cut glass fiber reinforced plastic wheel, said cut glass fibers being from 0.125 to 1.5 inches in length.
U.S. Pat. No. 5,277,479 discloses a resin wheel comprising a rim and a disk molded integrally, and the wheel is formed by injection molding a fiber-reinforced thermoplastic resin wherein the fiber-reinforced thermoplastic resin comprises short fibers (0.1-0.5 mm) and long-fibers (>1 mm).
US application publication 2012/0001476 discloses injection molded composite wheels comprising a polyimide composition.
Another problem with some metal alloys and some polymers is salt stress (induced) corrosion cracking (SSCC), where a part under stress undergoes accelerated corrosion when under stress and in contact with inorganic salts. This often results in cracking and premature failure of the part.
US Patent Publication 2010/0233402 entitled “Salt Resistant Polyamide Compositions” discloses certain semi-aromatic copolyamides that exhibit improved chemical resistance especially to metal halides and salts compared to corresponding aliphatic homopolyamides. In these copolyamides, at least 15 mole percent of the repeat units are derived from monomers that comprise an aromatic structure. Thus, semi-aromatic copolyamides 612/6T comprising 20 to 30 mole percent 6T units exhibit improved salt resistance than corresponding homopolyamide PA 612.
The presence of two or more types of repeat units in a copolyamide however typically has a negative consequence. These copolyamides have reduced degree of crystallinity. As a result they exhibit inferior high temperature properties compared to the corresponding homopolyamides. These properties include such mechanical properties as stiffness, strength and creep resistance at high temperature that are important in many of their end-uses. As the aromatic repeat unit content increases to approach 50 mole percent, the polymer becomes increasingly amorphous, and correspondingly exhibits greater loss in high temperature properties.
Furthermore, increasing petroleum raw material prices make it desirable to develop engineering polymers from linear, long chain dicarboxylic acids from renewable feedstocks. As such, there is a demand for renewable bio-based polymers having similar or better performance characteristics than petrochemical-based polymers. As example, renewable nylon materials such as PA 610 are based on ricinoleic acid derived sebacic acid (C10). However, ricinoleic acid production requires the processing castor beans and involves the handling of highly allergenic material and highly toxic ricin. Moreover, the production of sebacic acid is burdened with high energy consumption, a large amount of salt by product and other byproducts.
WO 2010/068904 discloses a method to produce renewable alkanes from biomass based triglycerides in high yield and selectivity and their fermentation to renewable diacids. Such naturally occurring triglycerides, also referred to as oils and fats, are composed of a variety of fatty acid chain lengths specific to the type of fat and oil. Most abundant amongst vegetable oils are triglycerides based on C12, C14, C16 and C18 fatty acids. Several vegetable oils are rich C12-C18 fatty esters including soybean oil, palm oil, sunflower oil, olive oil, cotton seed oil and corn oil (Ullmann's Encyclopedia of Technical Chemistry, A. Thomas: “Fats and Fatty Oils” (2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim; electronic version, 10.1002/14356007.a10 173). As such, dioic acid streams based on the oxidative fermentation of renewable alkanes derived from such oils, being rich in C12-C18 dioic acids, may be useful in formation of economically and environmentally attractive polymers.
Thus, desired are thermoplastic polymers that make use of renewable C12-C18 dioic acids. Also desired are thermoplastic compositions that have favorable properties for injection molding, provide high resistance to salt stress (induced) corrosion cracking, and exhibit high tensile modulus, that is, greater or equal to 8.5 Gpa, and high elongation at break, that is, greater or equal to 4% elongation at break. Such thermoplastic compositions would be especially useful in fiber reinforced wheels to provide the toughness is properties and salt resistance satisfactory for many vehicle applications.